I'm the head TA for '15-237: Building Cross Platform Mobile Web Apps' at Carnegie Mellon University, and I just happened to stumble upon your post and I think I may be able to help.
Once you're done, learn how to use the fairly simple HTML5 canvas API . At this point you should be able to build pretty much any browser-based, client-side-only game you like. Also, there are several libraries that build on the basic canvas API. I heard that Raphael.js is a good one.
It's sort of a long journey, but I think that going through it is going to be much more help than answering your specific questions directly.
Hope this helps!